Should USARTx->BRR have to re-calculate ?

[Carter Lee]

Posted on September 11, 2017 at 16:33

Hi,

Now I'm trying to implement UART function as the below,

But the problem is keep showing in RS232 Tool.

I'm just referring fully reference posting such as

https://community.st.com/thread/19577?commentID=48791#comment

There's no miss match. But I don't know what is the problem and how to resolve this.

Could you please any advice to resolve this problem?

I guess one thing is there's noUSARTx->BRR declaration.

Is this possible way to happen the problem??

USART_InitTypeDef USART_InitStructure;

int putcharx(int ch)

{

while (USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);

USART_SendData(USART1, (uint8_t)ch);

return ch;

}

int main(void)

{

RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);

RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);

//UART////////////////////////////////////////////////////////////////////////

/*-------------------------- GPIO Configuration ----------------------------*/

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);

/* Connect USART pins to AF */

GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1); // USART1_TX

GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1); // USART1_RX

USART_InitStructure.USART_BaudRate = 9600;

USART_InitStructure.USART_WordLength = USART_WordLength_8b;

USART_InitStructure.USART_StopBits = USART_StopBits_1;

USART_InitStructure.USART_Parity = USART_Parity_No;

USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;

USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

USART_Init(USART1, &USART_InitStructure);

USART_Cmd(USART1, ENABLE);

/////////////////////////////////////////////////////////////////////////////////

while (1)

{

USART_SendData(USART1, 0x49); // Send 'I' //TEST 2

}

In case TEST 1 and TEST2 have the same output result as the below image.

What am I supposed to do to resolve this problem?

should I have to calculate about

USARTx->BRR

?

Note: this post was migrated and contained many threaded conversations, some content may be missing.

[Tesla DeLorean]

Posted on September 11, 2017 at 16:50

Can we *PLEASE* keep all your USART related adventures in one thread? Your audience here is limited.

You would need to make sure HSE_VALUE is correctly defined for the board, perhaps in stm32f4xx_conf.h and be 8000000 and not 25000000. Check also that system_stm32f4xx.c configures the PLL with the expectation of an 8 MHz crystal and not a 25 MHz one.

Unless you change the bus speeds dynamically you shouldn't need to revisit USART->BRR

Send an 0x55 data pattern and confirm the bit timing with a scope. Don't send data to the register unless TXE is asserted, you'll just garble things.

[Carter Lee]

Posted on September 12, 2017 at 16:16

Clive, I'm struggling to receive data from PC with code below.

Sending data from STM32 board to PC is working good.

But receiving from PC has a problem.

The below image ,  I just prove the PA10 while sending data.

I'm not sure but would you please check this configuration?

void SendCharUSART1(char ch){

// Wait until TXE is set

while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET)

{

}

USART_SendData(USART1, ch);

// Wait until the end of transmit

while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET)

{

}

}

char GetCharUSART1(void){

char ch;

// Wait until the USART1 Receive Data Register is not empty

while(USART_GetFlagStatus(USART1, USART_FLAG_RXNE) == RESET)

{

}

ch = (USART_ReceiveData(USART1) & 0xFF);

return ch;

}

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1); // USART1_TX

GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1); // USART1_RX

USART_InitStructure.USART_BaudRate = 9600;

USART_InitStructure.USART_WordLength = USART_WordLength_8b;

USART_InitStructure.USART_StopBits = USART_StopBits_1;

USART_InitStructure.USART_Parity = USART_Parity_No;

USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;

USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

USART_Init(USART1, &USART_InitStructure);

USART_Cmd(USART1, ENABLE);

/////////////////////////////////////////////////////////////////////////////////

SYSCFG_EXTILineConfig(0x0,0);

...

SendCharUSART1(0x0D);

SendCharUSART1(0x0A);

SendCharUSART1('U');

SendCharUSART1('S');

SendCharUSART1('A');

SendCharUSART1('R');

SendCharUSART1('T');

SendCharUSART1('1');

SendCharUSART1('>');

// Get and echo USART1

ch = GetCharUSART1();

while (ch != 0x0D) {

SendCharUSART1(ch);

ch = GetCharUSART1();

}

What am I missing?

Currently, stuck in here  while(USART_GetFlagStatus(USART1, USART_FLAG_RXNE) == RESET)  

during sending the data from PC to eval board.

[Tesla DeLorean]

Posted on September 12, 2017 at 16:31

So you show me a static signal on the USART1_RX and ask why it receives nothing?

Is this pin clashing with the VCP? Did you disconnect the ST-LINK's USART from the STM32F429? Make sure SB15 is *REMOVED*